416 



THE INSECT WORLD. 



many processes : the injection of quicklime or of creosote, the 

 application of arsenical soap, &c. But it does not appear that 

 these processes are infallibly efficacious, nor, above all, easy to 

 employ. 



Among other Neuroptera which undergo incomplete meta- 

 morphoses we will mention, first, the genera Perla and Nemoura* 



Fig. 383. Larva of Perla 

 bicaudata. 



Fig. 384. Larva of a 

 Nemoura. 



Fig. 385. Perla marginata 

 (larva). 



(Figs. 383, 384, and 385), which flutter about the banks of rivers, 

 and settle on stones, shrubs, and aquatic plants. Their larvae are 

 naked, without cases, and always live in the water, hiding themselves 

 un,der stones, 'to watch for small insects, for they are carnivorous. 

 One sees them often balancing their bodies, holding on to a pebble. 

 They go through the winter, and only become pupae in the spring. 

 After moulting, they have the rudiments of wings. Very soon 

 afterwards the pupae leave the water, and undergo their meta- 

 morphosis. The adult lives only a few days, for its mouth is not 

 suited for receiving food. The larvae have, at the end of their 

 bodies, two long threads, which remain in the perfect Perla, but 

 not in the perfect Nemoura ; the latter lose the two caudal hairs 



* From vrjfjia, a thread ; and ovpd, a tail. ED. 



